# Research Overview

I am a physicist specializing in astrophysics and cosmology, focusing on black holes, neutron stars, and gravitational-waves. I have published on a diverse set of topics, including dark matter, dark energy, gamma-ray bursts, cosmological structure formation and N-body simulations, neutron stars, black holes, supernovae, the first stars, compact-object population synthesis, numerical relativity, and gravitational lensing.

My gravitational-wave work includes the first paper on counterpart standard sirens (where Scott Hughes and I introduce the name “standard sirens” to describe a novel gravitational-wave probe of cosmology, building on the visionary 1986 paper by Bernie Schutz), the first paper forecasting the critical role of standard sirens in cosmology, paper 1 and paper 2 introducing spectral sirens (which we argue will likely become one of the most powerful precision probes of cosmology), the first dark siren analysis, the first paper showing that black holes merged more frequently in the early universe, the first paper pointing out that big black holes are missing, an independent discovery of the electromagnetic counterpart to GW170817, a paper arguing for black hole spin as a clean discriminator of formation channels, a paper using GW170817 to measure the number of spacetime dimensions, the first population synthesis model for GW150914, a paper asking whether LIGO black holes are built out of smaller black holes, a paper clarifying black hole shadows (especially applicable to Event Horizon Telescope images of supermassive black holes), a paper arguing that the earliest supermassive black holes had supermassive seeds, and the first paper examining how black holes pair up (demonstrating that black holes are “picky” about their partners).

I am also a member of the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration, and have made significant contributions to a number of LIGO results, including: the discovery of GW150914 (Weiss, Thorne, and Barish were awarded the Nobel prize for this discovery), the discovery of GW170817 (the most observed astronomical transient in history), the first standard siren (confirming our earlier prediction), the first gravitational-wave multi-messenger source, the O2 and O3 gravitational-wave populations (the definitive papers in gravitational-wave astrophysics), and the O3 cosmology paper (the authoritative paper in gravitational-wave cosmology, implementing analysis methods my group has helped pioneer).

This is a small selection of my work; a full list, including recent papers, can be found here.

**The first standard siren measurement of the age of the Universe:**GW170817 measurement of the Hubble constant,

*H*

_{0}. The marginalized posterior density for

*H*

_{0},

*p*(

*H*

_{0}| GW170817), is shown by the blue curve. Constraints at 1

*σ*(darker shading) and 2

*σ*(lighter shading) from Planck

^{20}and SHoES

^{21}are shown in green and orange, respectively. The maximum a posteriori value and minimal 68.3% credible interval from this posterior density function is . The 68.3% (1

*σ*) and 95.4% (2

*σ*) minimal credible intervals are indicated by dashed and dotted lines, respectively.

### CV & Publications

Most of my papers are freely available from Google Scholar, ADS (astro), INSPIRE (HEP), and the Los Alamos arXiv.

- Daniel Holz CV
- Publications (excluding LIGO collaboration papers)
- All Publications

**Then felt I like some watcher of the skies**

**When a new planet swims into his ken;**

**Or like stout Cortez when with eagle eyes**

**He star’d at the Pacific–and all his men**

**Look’d at each other with a wild surmise–**

**Silent, upon a peak in Darien.**

John Keats, *On First Looking into Chapman’s Homer*